Illuminating device with a rechargeable battery or a mains supply power source

ABSTRACT

This disclosure relates to an illuminating device, primarily for use as a book reader, in which a slightly tapering transparent sheet is illuminated edgewise by low-intensity lamps in a housing extending along its thicker edge. The sheet is placed flat against the book page to be read, the page being illuminated by light internally reflected from the front surface of the transparent sheet and being read through the transparent sheet. Circuits are described for alternatively energizing the lamps from the mains supply and a rechargeable battery.

United States Patent [72] Inventor Stanley Balfour-Lynn 6a Palace Gate,London, W.8., England [21] Appl. No. 751,578 [22] Filed Aug. 9, 1968[451 Patented Nov. 2, 1971 [54] ILLUMINATING DEVICE WITH A RECHARGEABLEBATTERY OR A MAINS SUPPLY POWER SOURCE 10 Claims, 6 Drawing Figs.

[52] US. Cl 240/1 R, 240/2 R, 240/10.6 R [51] lnt.Cl F211 [50] Field ofSearch 240/] El, 2 D, 37.1,10.6 R, 37, 2 P, 1.64 NB; 320/11; 315/206,363, 50, 51, 90, 92; 317/156 [56] References Cited UNITED STATES PATENTS1,791,156 2/1931 Beetem 320/11 2,358,203 9/1944 Best 240/2 P 2,465,1143/1949 Oury 240/10.6S 3,132,810 5/1964 Ostensen 240/1 El PrimaryExaminer-Samuel S. Matthews Assistant Examiner-T. A. MauroAttorney-Holcombe, Wetherill & Brisebois ABSTRACT: This disclosurerelates to an illuminating device, primarily for use as a book reader,in which a slightly tapering transparent sheet is illuminated edgewiseby low-intensity lamps in a housing extending along its thicker edge.The sheet is placed flat against the book page to be read, the pagebeing illuminated by light internally reflected from the front surfaceof the transparent sheet and being read through the transparent sheet.Circuits are described for alternatively energizing the lamps from themains supply and a rechargeable battery.

ILLUMINATING DEVICE WITH A RECIIARGEABLE BATTERY OR A MAINS SUPPLY POWERSOURCE The present invention relates to an illuminating device forenabling books and other documents to be read or viewed in a dark roomwithout producing substantial illumination in the room. The device isparticularly suitable for enabling a person to read in bed at night, forexample at home or in hospitals, with the minimum of interference withother persons sleeping or resting in the same room. The illuminatingdevice according to the invention consists of a generally rectangularsheet of transparent material of a convenient size to cover the whole'ora part of the page of a book or other document to be read, said sheettapering slightly in thickness from one edge to the opposite edge, and ahousing containing one or more low voltage low-intensity lamps disposedalong the thicker edge of the sheet and arranged to illuminate said edgeof the sheet, the arrangement being such that the light projected intothe sheet is internally reflected from a surface thereof (hereinafterreferred to as the upper surface) so that at least a part of the lightpasses out of the sheet through the other surface thereof (hereinafterreferred to as the lower surface) said lower surface being free fromobstruction so that it can be placed flat against the page of the bookor surface of the document to be read.

By means of this device the page can be substantially uniformlyilluminated so that it can be read by looking through the transparentsheet, while scattered light in the room remains low. In fact the mainproportion of light which is scattered in the room arises fromreflection from the page being read, so that by keeping the intensity ofthe light low and sufficient only to enable easy reading withouteye-strain the amount of scattered light can be kept to the minimum. Theedges of the sheet other than where the light passes thereinto may berendered opaque by painting or in any other convenient manner in orderto avoid light from leaving the device other than through the upper andlower surfaces of the sheet.

The lamp or lamps in the housing of the device may be energized from themains supply through a stepdown transformer, or they may be energizedfrom a battery contained in the housing or in a separate casing. 7

According to the feature of the invention the device is adapted to beenergized from the mains through a stepdown transformer and alsoincorporates a battery which serves the purpose of an alternative sourceof electric supply when a mains supply is not available and/or foreffecting remote switching on and off of the mains supply. Preferablythe battery is of the rechargeable type and is connected so as to bechargeable from the mains supply when the lamps are being illuminatedfrom the mains supply and/or when the device is not in use but is stillconnected to the mains supply.

A further feature of the invention consists in providing the device witha mirror surface to enable it also to be used as a mirror.

In order that the invention may be more clearly understood, referencewill now be made to the accompanying drawings, in which:

FIG. 1 is a perspective view of one embodiment of a book pageilluminating device according to the invention.

FIG. 2 is a section through the housing of the device along the line A-AofFIG. l.

FIG. 3 is a scrap view of the housing.

FIGS. 4 and 5 are two circuit diagrams.

FIG. 6 is a sectioned perspective view of a picture illuminating deviceaccording to the invention.

Referring to FIGS. l-3, the device comprises a sheet 1 of a transparentmaterial, conveniently a transparent plastics material such as knownunder the Registered Trademark Perspex. Along one edge of the sheet issecured an opaque housing 2 which contains one or more small electriclamps 9, such as lamps as used in hand torches, for illuminating thesheet edgewise. The upper surface 1a of the sheet slopes towards thelower surface lb in the direction away from the illuminated edge, andthe arrangement is such that some of the light entering the sheet willbe reflected internally from the upper surface and out through the lowersurface to illuminate the page to be read, against which the lowersurface of the sheet is laid flat when the device is in use. The otheredges, 3, 4 and 3 of the sheet are rendered opaque, for example bypainting. A convenient size for the sheet is 8%"X5", and it may be aboutV4" thick adjacent the housing 2 and taper to about l/l6 at its otherend.

The lamps are energized from the electric mains supply through astepdown transformer contained in a casing 6 provided with contacts 5for plugging it into a conventional mains lighting socket, and isconnected to the lamps 9 by a flexible cable 7, preferably provided withplug-in connections 10,11. The housing 2 may carry an appropriatecontrol switch or switches 12.

In order to reduce the temperature to which the housing 2 is heated bythe heat generated by the lamp or lamps 9, the housing may be providedwith ventilating apertures 8, preferably disposed in the wall of thehousing at positions above and below the lamp or lamps when the sheet issubstantially horizontal, baffles being provided to prevent light fromthe lamps passing out of the housing through the ventilation apertures.As shown in the drawing, the baflles are constructed as reflectors 13 toguide light from the lamps 9 towards the edge of the transparentsheet 1. Alternatively separate reflectors for this purpose may beprovided in the housing. The housing 2 is also shown as accommodating abattery 17 in a compartment 18 accessible by removing the end cap 2a ofthe housing. The compartment 18, reflectors l3 and holders for the lamps9 may be assembled on a spine or frame 19 and removable as a unit fromthe housing 2 for servicing or lamp replacement. The spine or frame maybe conveniently carried on the other end cap 2b of the housing andremovable therewith. The switch or switches 12, or at least the contactsthereof, is/are preferably removable with the spine or frame and mayconveniently be mounted on the end cap 2b.

The battery 17 is preferably of the rechargeable type and connected in acircuit so that it is rechargeable from the output of the mainstransformer. The battery can be used as an alternative source of supplyfor the lamps, when a mains supply is not available. It is desirable, ifthe device is to be usedfor reading while in bed, and especially so ifthe user is a patient in a hospital, that the lamps may be switched offwithout the user having to get out of bed to switch off the mains switchin order to render the device safe."

One suitable form of circuit is shown in FIG. 4 in which the battery 17is connected in series with a diode 20 and resistor 21 across theterminals 10a, 10b into which the plug 10 at one end of the cable 7 isinserted, the plug 11 at the other end of the cable being inserted intothe terminals 11a, 11b on the easing 6 containing the stepdowntransformer 22. The lam'p'9 is connectable across the battery 17 whenthe switch 12 is closed.

With the circuit described, the output from the transformer 22 isrectified by the diode 20 and charges the battery. When the switch 12 isclosed the lamp 9 is illuminated from the battery, irrespective ofwhether or not it is being simultaneously charged from the mains. Withthe circuit described there is always the battery charging load acrossthe output of the transformer so that the transformer will not overheator burn out if the lamp is switched off and the mains switch is left on.

FIG. 5 shows another circuit in which the'battery is used for the remotecontrol of switching on and ofi of the mains supply to the transformer.To this end the casing 6 also contains a relay 23 having normally opencontacts 23a in the circuit to the primary winding of the transformer 22and the cable 7 contains a third wire connecting a terminal Us on thecasing 6 to a terminal 10c on the housing 2. The relay 23 is bridgedacross the terminals 11a, 11c and is also connected in series with thesecondary winding of the transformer across the terminals 11a, 11b.Terminal 10c is connected through a normally open contact 12a to thejunction between the diode 20 and the battery 17. Between the terminal10a and the other pole of the battery 17 is a normally closed contact12b. The switch 12 has a third position in which it connects the lamp 9to the terminal 10b.

With the circuit of FIG. 5, by momentarily closing contact 12a thebattery 17 is connected across the relay 23 which energizes and closesits contact 230. The transformer is thus connected to the mains supplyand the resulting current in the secondary circuit through the chargingdiode 20 and the battery 17 holds the relay 23 energized when contact12a is opened. When the switch 12 is in its lowermost position the lamp9 is energized direct from the mains and the battery is simultaneouslycharged. in the central position of switch 12, only battery chargingtakes place and the lamp 9 is extinguished. In the upper position of theswitch 12 the lamp 9 is energized from the battery 17 which issimultaneously being charged. By opening contact 12b the circuit throughthe relay 23 is opened and consequently its contacts 23a open and themains supply to the transformer is cut off. The contacts 12a, 12b, whichare conveniently pushbutton operated, thus effect remote control of themains supply to the transformer. When the mains supply is cut off, andalso when the device is not connected to the transformer, the lamps 9can still be illuminated by the battery by turning the switch 12 to itsupper position.

if a nonchargeable battery is used, the circuit may be similar to thatshown in FIG. 5 but the diode 20 and resistor 21 would then be omitted.

in order that the lower surface of the sheet 1 may be placed flatagainst the page to be read, it must be kept free from obstruction. Evenif the sheet is lifted only a short distance away from the surface ofthe page the intensity of illumination of the page is seriously reducedin view of the low intensity of the light from the lamps. If desired thedevice may be provided with a clip for clipping the device on to a pageof the book. This clip may itself comprise a bacltplate M of thin rigidmaterial of substantially the same size as the sheet 1 so that the pageto be read is held flat between the sheet 1 and the backplate 14. Thebackplate may be pivoted to the housing 2 by pivots 15, and the sheetand backplate may be urged together by a spring 16.

The backplate 14 may have a mirror surface, or carry a mirror, on eitheror both its front and rear surfaces, so that the device can be used as amirror as well as a book reader. The backplate 14 may be of sheet metalwith a highly polished or plated surface.

If desired the upper surface of the sheet may be silvered or treated toform a semitransparent mirror surface. This assists in increasing theillumination of the page and also enables the device to be used as amirror.

The surfaces of the sheet 1 may be processed or coated to possessantistatic and/or antiscratch properties.

It will be appreciated that the device, instead of being used as a bookreader, can be used for illuminating other documents or surfaces to beviewed instead of read, such as pietures, paintings or photographs. Itis only necessary to mount the picture behind the sheet 1. The housingcontaining the lamps may, as shown in FIG. 6, be constructed as part ofapicture frame 24 of which the sheet forms the front glass behind whichthe picture or photograph is mounted. The frame may be provided withmeans for hanging it on a wall or supports for standing it on a surface.The frame may incorporate a rechargeable battery as above described, sothat the frame can be stood or hung in any desired position, andilluminated, without it being necessary to have an electric cableleading thereto while it is illuminated.

While particular embodiments have been described, it will be understoodthat various modifications may be made without departing from the scopeof the invention. For example, instead of being made of a transparentplastics material, the sheet 1 may be made of glass. Moreover, therectifier and resistor of the charging circuit may be incorporated inthe casing 6 instead of in the housing 2.

lclaim:

1. An illuminating device comprising a generally rectangular sheet oftransparent material of which both opposite surfaces are flat smooth andpolished, said sheet tapering slightly in thickness from one edge to athinner opposite edge, and a housing containing at least one low-voltagelow-intensity lamp disposed along the thicker edge of the sheet andarranged to illuminate said edge of the sheet, the arrangement beingsuch that the light projected into the sheet is internally reflectedfrom one surface thereof so that a part of the light passes out of thesheet through the other surface thereof, said other surface being freefrom obstruction so that it can be placed flat against a surface to beilluminated with only low light intensity sufiicient to enable it to beviewed by looking through the transparent sheet.

2. A device as claimed in claim 1, wherein the housing is provided withapertures to allow air to circulate therethrough to cool said at leastone lamp and the housing, light baffles preventing any substantialamount of light from being emitted through said apertures.

3. A device as claimed in claim 1 in combination with a stepdown mainstransformer having primary and secondary windings, a flexible cableconnecting said secondary winding to the device to provide current forenergizing said at least one lamp, a battery as an alternative source ofcurrent for said at least one lamp, and a relay which is assembled as aunit with the transformer and is connected in circuit with saidsecondary winding and, when energized, closes normally open contacts inthe circuit to the primary winding of the transformer, and a remotecontrol switch which, when closed, completes a circuit from the batteryand through the flexible cable to energize the relay, the relayremaining energized, when said switch is reopened, so long as thesecondary current flows therethrough.

4. A device as claimed in claim 3, wherein said battery is rechargeableand a rectifier is provided connectable in a circuit in series with thebattery and said secondary winding for charging the battery, and thehousing carries a switch for connecting said at least one lamp acrossthe poles of the battery.

5. A device as claimed in claim l, in combination with a stepdown mainstransformer having a primary and a secondary winding, a flexible cableconnecting said secondary winding to the device to provide current forenergizing said at least one lamp, a rechargeable battery in series witha charging rectifier connected across said secondary winding in parallelwith said at least one lamp, and a relay which is assembled as a unitwith the transformer and when energized, closes normally open contactsin the circuit to the primary winding of the transformer, a remotecontrol switch which, when closed, completes a circuit from the batteryand through the flexible cable to energize the relay, said relay beingconnected with said secondary winding so as to remain energized, whensaid switch is reopened, so long as the secondary current flows.

6. An illuminating device as claimed in claim 4, and including means forassisting dissipation of the heat generated by said at least one lamp; aframe carrying said at least one lamp, a compartment for said batteryand said switch and the associated electrical connections and forming asubassembly insertable as a unit in said housing; means rendering opaquethe edges of said transparent sheet other than said thicker edge.

7. A device as claimed in claim 6, wherein the housing is provided withapertures to allow cooling air to circulate therethrough, and at leastone light baffle for preventing substantial escape of light through saidapertures, said at least one baffle constituting a reflector fordirecting light from said at least one lamp towards the edge of thetransparent sheet and being carried by said frame, and wherein said onesurface of the transparent sheet is formed as a semitransparent mirror.

8. A device as claimed in claim 1, wherein said at least one lamp, acompartment for housing a battery, a control switch and the associatedelectrical circuitry and connections are carried on a frame insertableas a unit into said housing.

9. A device as claimed in claim ll, wherein a backplate is providedadjacent said other surface of the transparent sheet 3 ,617 ,727 5 6 forholding a sheet to be illuminated close against said other 10. A deviceas claimed in claim 1, wherein the housing surface, said backplate beingpivoted to the housing and being forms part of a picture frame of whichthe transparent sheet urged by a spring towards said other surface ofthe sheet, and forms the from glassy and means mounting a I Or the atleast one of the surfaces of said bacitplate comprising a mir- 5 likeagainst the rear Surface of the tmmpaw'nt sheet or t i l

1. An illuminating device comprising a generally rectangular sheet oftransparent material of which both opposite surfaces are flat smooth andpolished, said sheet tapering slightly in thickness from one edge to athinner opposite edge, and a housing containing at least one low-voltagelow-intensity lamp disposed along the thicker edge of the sheet andarranged to illuminate said edge of the sheet, the arrangement beingsuch that the light projected into the sheet is internally reflectedfrom one surface thereof so that a part of the light passes out of thesheet through the other surface thereof, said other surface being freefrom obstruction so that it can be placed flat against a surface to beilluminated with only low light intensity sufficient to enable it to beviewed by looking through the transparent sheet.
 2. A device as claimedin claim 1, wherein the housing is provided with apertures to allow airto circulate therethrough to cool said at least one lamp and thehousing, light baffles preventing any substantial amount of light frombeing emitted through said apertures.
 3. A device as claimed in claim 1in combination with a stepdown mains transformer having primary andsecondary windings, a flexible cable connecting said secondary windingto the device to provide current for energizing said at least one lamp,a battery as an alternative source of current for said at least onelamp, and a relay which is assembled as a unit with the transformer andis connected in circuit with said secondary winding and, when energized,closes normally open contacts in the circuit to the primary winding ofthe transformer, and a remote control switch which, when closed,completes a circuit from the battery and through the flexible cable toenergize the relay, the relay remaining energized, when said switch isreopened, so long as the secondary current flows therethrough.
 4. Adevice as claimed in claim 3, wherein said battery is rechargeable and arectifier is provided connectable in a circuit in series with thebattery and said secondary winding for charging the battery, and thehousing carries a switch for connecting said at least one lamp acRossthe poles of the battery.
 5. A device as claimed in claim 1, incombination with a stepdown mains transformer having a primary and asecondary winding, a flexible cable connecting said secondary winding tothe device to provide current for energizing said at least one lamp, arechargeable battery in series with a charging rectifier connectedacross said secondary winding in parallel with said at least one lamp,and a relay which is assembled as a unit with the transformer and whenenergized, closes normally open contacts in the circuit to the primarywinding of the transformer, a remote control switch which, when closed,completes a circuit from the battery and through the flexible cable toenergize the relay, said relay being connected with said secondarywinding so as to remain energized, when said switch is reopened, so longas the secondary current flows.
 6. An illuminating device as claimed inclaim 4, and including means for assisting dissipation of the heatgenerated by said at least one lamp; a frame carrying said at least onelamp, a compartment for said battery and said switch and the associatedelectrical connections and forming a subassembly insertable as a unit insaid housing; means rendering opaque the edges of said transparent sheetother than said thicker edge.
 7. A device as claimed in claim 6, whereinthe housing is provided with apertures to allow cooling air to circulatetherethrough, and at least one light baffle for preventing substantialescape of light through said apertures, said at least one baffleconstituting a reflector for directing light from said at least one lamptowards the edge of the transparent sheet and being carried by saidframe, and wherein said one surface of the transparent sheet is formedas a semitransparent mirror.
 8. A device as claimed in claim 1, whereinsaid at least one lamp, a compartment for housing a battery, a controlswitch and the associated electrical circuitry and connections arecarried on a frame insertable as a unit into said housing.
 9. A deviceas claimed in claim 1, wherein a backplate is provided adjacent saidother surface of the transparent sheet for holding a sheet to beilluminated close against said other surface, said backplate beingpivoted to the housing and being urged by a spring towards said othersurface of the sheet, and at least one of the surfaces of said backplatecomprising a mirror.
 10. A device as claimed in claim 1, wherein thehousing forms part of a picture frame of which the transparent sheetforms the front ''''glass,'''' and means mounting a picture or the likeagainst the rear surface of the transparent sheet.